Production of cellulose ethers using a premix of alkali and etherifying agent

Abstract

A process for the preparation of a cellulose ether by reacting in a heterogenous reaction mixture an alkaline solution and an etherifying agent with a fibrous cellulose. The total of the required stoichiometric amount of the alkaline solution and at least a portion of the etherifying agent required in producing the cellulose ether are admixed (e.g. in a mixing nozzle) at sufficiently low temperature to suppress reaction between the alkaline solution and the etherifying agent. The admixture is then contacted with the cellulose fibers, preferably by spraying the admixture thereupon. Additional of the etherifying agent if required is then added to the reaction mixture, and the heterogenous reaction mixture is agitated and reacted at an initial temperature below 40° C. sufficient to produce alkalization of the cellulose. Thereafter the temperature is increased above 40° C., preferably incrementally or gradually up to about 100° C., preferably to 80° C., to produce etherification of the cellulose and form the cellulose ether.

Having described the invention, what is claimed is: 
     
       1. In a process for the preparation of a cellulose ether in an alkalization stage wherein an alkaline solution is sprayed upon and reacted with a powdered fibrous cellulose to form an alkali cellulose, and an etherification stage wherein an etherifying agent, in admixture with the alkali cellulose, essentially as a damp powder, is agitated and reacted to form a cellulose ether product, the improvement comprising,   introducing into and premixing in a nozzle the total of the required stoichiometric amount of the alkaline solution and at least about 25 percent of the stoichiometric amount of the etherifying agent required in producing the cellulose ether, while maintaining the admixture at a temperature sufficient to suppress reaction between said alkaline solution and said etherifying agent,   withdrawing said admixture as a spray containing atomized droplets of said alkaline solution from the mixing nozzle,   spraying said admixture of alkaline solution and etherifying agent upon the cellulose at an initial temperature sufficient to produce alkalization of the cellulose, while agitating said cellulose in said reaction mixture inclusive of the stoichiometric amounts of the alkaline solution, etherifying agent and cellulose as a damp powder, and thereafter increasing the temperature of the reacting mixture to form the cellulose ether.   
     
     
       2. The process of claim 1 wherein the etherifying agent is premixed with the alkaline solution, prior to spraying said admixture upon the cellulose, in concentration ranging from about 25 percent to about 100 percent of the stoichiometric amount of the etherifying agent required in the reaction. 
     
     
       3. The process of claim 2 wherein the etherifying agent is premixed with the alkaline solution in concentration ranging from about 25 percent to about 50 percent. 
     
     
       4. The process of claim 1 wherein the alkalization reaction is conducted at a temperature ranging from about 20° C. up to 40° C., and the etherification reaction is conducted at temperature ranging above 40° C. to about 100° C. 
     
     
       5. The process of claim 4 wherein the temperature of the etherification reaction ranges from above 40° C. to about 80° C. 
     
     
       6. The process of claim 1 wherein the temperature of the alkalization reaction ranges from about 20° C. up to 40° C. and this temperature is maintained for a period ranging from about 0.1 hour to about 0.25 hours sufficient to substantially complete alkalization of the cellulose, and thereafter the etherification reaction is conducted by incrementally or gradually increasing the temperature above 40° C. to about 100° C., and the peak temperature is maintained over a period of from about 0.5 hour to about 2 hours. 
     
     
       7. The process of claim 6 wherein the temperature of the alkalization reaction ranges from about 20° C. to about 30° C., and the temperature of the etherification reaction ranges from about a low of about 40° C. to a high of about 80° C. 
     
     
       8. The process of claim 7 wherein the alkalization reaction is conducted over a period ranging from about 0.15 hour to about 0.20 hours, and the peak temperature of the etherification reaction is maintained over a period of from about 0.75 hour to about 1.25 hours. 
     
     
       9. The process of claim 1 wherein the cellulose ether produced is methyl cellulose, the methyl cellulose having been produced by reaction between the cellulose, methyl chloride and an alkali metal hydroxide. 
     
     
       10. The process of claim 1 wherein the cellulose ether produced is, methylethylhydroxypropylhydroxycellulose, the methylethylhydroxypropylhydroxycellulose having been produced by reaction between the cellulose an admixture of ethylene oxide, propylene oxide and methyl chloride and an alkali metal hydroxide. 
     
     
       11. In a process for the preparation of a cellulose ether product in an alkalinization stage wherein an alkali metal hydroxide solution is sprayed upon and reacted with a powdered fibrous cellulose to form an alkali cellulose, and an etherification stage wherein an etherifying agent comprised of methyl chloride, in admixture with the alkali cellulose, essentially as a damp powder, is agitated and reacted to form a cellulose ether product, the improvement comprising,   introducing into and premixing in a mixing nozzle the total of the required stoichiometric amount of the alkali metal hydroxide solution and at least about 25 percent of the stoichiometric amount of the methyl chloride etherifying agent required in producing the cellulose ether, while maintaining the admixture at a temperature sufficient to suppress reaction between said alkali metal hydroxide solution and said methyl chloride etherifying agent,   withdrawing said admixture as a spray containing atomized droplets of the alkali metal hydroxide from the mixing nozzle,   spraying said admixture of alkali metal hydroxide solution and methyl chloride etherifying agent upon the cellulose at an initial temperature sufficient to produce alkalization of the cellulose, while agitating said cellulose in said reaction mixture inclusive of stoichiometric amounts of the alkali metal hydroxide solution, methyl chloride etherifying agent and cellulose as a damp powder, and thereafter increasing the temperature of the reacting mixture to form the methyl cellulose ether.   
     
     
       12. The process of claim 11 wherein the alkalization reaction is conducted at a temperature ranging from about 20° C. up to 40° C., and the etherification reaction is conducted at temperature ranging above 40° C. to about 100° C. 
     
     
       13. The process of claim 12 wherein the temperature of the etherification reaction ranges from above 40° C. to about 80° C. 
     
     
       14. The process of claim 11 wherein the temperature of the alkalization reaction ranges from about 20° C. up to 40° C. and this temperature is maintained for a period ranging from about 0.1 hour to about 0.25 hours sufficient to substantially complete alkalization of the cellulose, and thereafter the etherification reaction is conducted by incrementally or gradually increasing the temperature above 40° C. to about 100° C., and the peak temperature is maintained over a period of from about 0.5 hour to about 2 hours. 
     
     
       15. The process of claim 14 wherein the temperature of the alkalization reaction ranges from about 20° C. to about 30° C., and the temperature of the etherification reaction ranges from about a low of about 40° C. to a high of about 80° C. 
     
     
       16. The process of claim 15 wherein the alkalization reaction is conducted over a period ranging from about 0.15 hour to about 0.20 hours, and the peak temperature of the etherification reaction is maintained over a period of from about 0.75 hour to about 1.25 hours. 
     
     
       17. The process of claim 11 wherein the cellulose ether produced is methylethylhydroxypropylhydroxycellulose, the methylethylhydroxypropylhydroxycellulose having been produced by reaction between the cellulose, an admixture of ethylene oxide, propylene oxide and methyl chloride and an alkali metal hydroxide.